1. Field of the Invention
Methods and apparatuses consistent with present invention relate to data tracking in a data storage system, and detecting probe position error in a data storage system using a probe.
2. Description of the Related Art
Recently, scanning probe microscopy (SPM) has been adapted to a data storage system. In general, the data storage system using scanning probe microcopy has the following construction in order to implement a high recording density.
The data storage system using the scanning microscopy comprises: a data storage medium on which data is recorded, a probe having tips which contact with or are in a close proximity to the data storage medium to read and write data thereon and cantilevers supporting the tips, an XY stage (a scanner) moving the data storage medium, a controller for controlling the data storage system, and a signal processing unit. In addition, in order to read and write data on the data storage medium having the high recording density, a data tracking method needs to be performed in a higher resolution than a size of a data pit.
Conventionally, three types of data tracking methods have been used for the high-density data storage system using the scanning probe microscopy.
In a first type of data tracking method, in addition to the data signal read and written on the data storage medium, a mechanical or electrical signal is used for the data tracking. Examples of the first type are disclosed in U.S. Pat. Nos. 5,132,934, 5,396,483, 5,856,967, and 6,370,107, wherein metal patterns or mechanically-curved structures are formed on the data storage medium. However, it is difficult to accurately adjust the metal patterns and the mechanically-curved structures. In addition, since the mechanically-curved structures are used for a reading/writing mechanism, the first type of data tracking method is not practical.
In a second type of data tacking method, a probe or a data storage medium vibrate to modulate centers of data pits on the data storage medium. An example of the second type is disclosed in U.S. Pat. No. 5,404,349, wherein the data storage medium vibrates at a high frequency, and modulation and demodulation are adapted. However, it is difficult to vibrate the data storage medium at the high frequency. In addition, since the modulation and demodulate are used, the associated detecting circuitry is so complex that there is time delay in detection.
In a third type of data tacking method, relative displacement of centers of data pits on a data storage medium and a probe for reading and writing data are used for the data tracking. Examples of the third type are disclosed in U.S. Pat. Nos. 5,202,879 and 6,195,313, wherein it is necessary to accurately record the data patterns on the data storage medium. In particular, in U.S. Pat. No. 5,202,879, since the data pits can not continuously tracked, a tracking velocity is very low. Therefore, the data tracking method is vulnerable to external disturbance.